In some applications, and in particular in aeronautics, and more particularly in the manufacture of undercarriages or landing gear, it is sometimes necessary to place parts, such as force sensors, for example, on such landing gear in order to measure the deformations to which various parts of the landing gear are being subjected. This possibility is provided, in particular, for forestalling various kinds of failure, and even, for measuring the total weight of an aircraft.
Of all these applications, one is of particular interest, namely measuring the total mass of an aircraft and/or its center of gravity and/or the stress to which its tires are subjected. This can be done, for example, by measuring the deformation of an axle in the aircraft landing gear. The axle may be constituted by a hollow cylindrical part, in which case, electromagnetic or capacitive sensors may be placed inside the axle to measure the deformation thereof and thus to enable the forces applied to the landing gear to be deduced. By analyzing a set of such forces, the mass of the aircraft can readily be deduced. This is of particular interest just prior to take off to see if the total starting weight is acceptable.
The problem to be solved is how to place such sensors inside an axle. Techniques known up to now have always suffered from drawbacks.
Two particular prior art techniques require:
Either providing at least two bearing regions on the axle for engaging sensor-supporting parts, with the bearing force resulting from the radial resilience of the axle and from screw displacement of one or more moving parts on the sensor-supporting part. Since the radial resilience of the axle is small, the bearing force is concentrated and varies greatly when the axle is deformed under load, which is a potential source of breakage and of accident.
Otherwise, cavities are made in the axle and balls are received in the cavities. The same problem of potential stress concentrations leading to cracking and breakage remains.
Preferred implementations the present invention mitigate these drawbacks by ensuring that the pressure applied in the bearing regions remains practically constant in spite of possible deformation of the axle. This is achieved by using highly resilient bearing rings for supporting items such as deformation sensors. Further, stress concentrations are avoided.